When the condenser is in the DF or BF position the objectives can
be used for either darkfield or bright field. For phase contrast, the
condenser position should match the objective used. Meaning
that when the condenser is in position “40” the objective used
should also be 40x
•
Rotate 10× infinity plan phase contrast objective into the
field of view, then set the condenser to match the objective
(marker “10/20”)
•
Take the eyepiece out of the tube and insert the centering telescope in its place. Observed from centering
telescope, the dark and bright ring images should coincide with each other as shown in the figures below. If the
ring images can’t be observed clearly, first try and focus the centering telescope. If this does not solve the issue
raise or decline the condenser
•
If the bright ring and dark ring images are not coincided as shown below, adjust the position of the ring with the
two screw keys on the side of the condenser to move the ring until bright and dark ring images superimpose.
Repeat for all objectives/Zernike disc positions
Not centered
Centered properly
6.4 Centering the phase rings
The Zernike phase disc has five positions:
•
“DF” for darkfield observation (up to 400x),
•
“BF” for brightfield observation, this position also has an iris diaphragm
•
And “10/20”, “40” “100” which are corresponding to phase contrast observation using 10×, 20×, 40×, 100×
objectives respectively
Centration screws
Zernike condenser position indication
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